Carburetor



Sept. 26, 1961 J. o. SARTO 3,001,774

CARBURETOR Filed Dec. 1, 1958 INVENTOR. clORMH O. Q9HR T0.

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Unite of' Delaware Filed Dec. 1, 1958, Ser. No. 777,418

11 Claims. (Cl. 261-39) This. invention relates to downdraft carburetor construction and in particular to fuel feed control means therefor.

In downdraft carburetors of the conventional type employinga main air intake passage with throttle and choke valves therein, the problem exists of providing too rich a fuel mixture for the engine during idle and slow. speeds and at engine operating temperatures which maintains the thermostatically operated choke valve in a substantially closedpcsition. The closed position of the choke valve in these carburetors represents the necessity for a rich fuehmixture particularly for cold starting of the engine which rich mixture is obtained by the establishment. of apressure drop across the choke valve tending tosuck additional fuel for cold startingfrom the main fuel jet connecting the fuel bowl with the air intake passage.

During cold, cranking at substantially closed choke position the volume of air pumped by the engine is relatively low and the vacuum created downstream of the main fuel jet is of the correct magnitude for sucking the correct cold starting fuel supply through. the main jet. After the engine has started, however, and attains idle speed or speeds slightly in excess thereof, the volume of air pumped by the engine is increased significantly to reduce the air pressure dcwnstreamof the substantially closed choke valve to cause a quantity of fuel to be sucked from the main fuel port in excess of that required for eflicient engine performance. This excess fuel causes over-enrichment of the air-fuel combustion mixture at said low engine speeds and causes erratic-and improper functioning of the engine. it is desirable, therefore, to provide a means to adjust the pressure differential between the fuel bowl and the air intake passage section downstream of the choke blade during the aforesaid low engine speed operation.

It is therefore a major object of this invention to provide a fuel feed control means in a typical automatic choke downdraft carburetor for adjusting the pressure diiferential across the main fuel jet thereof during idle and light load conditions at substantially closed choke position to prevent over-enrichment of the combustion mixture, and also to provide a cooperating mechanism for circumventing this control means when it becomes necessary, such as during rapid acceleration, to suddenly provide a relatively high pressure drop across the main fuel jet.

In the present invention this object is accomplished by providing fluid passage means for connecting the fuel bowl air section and the intermediate pressure portion of the intake air passage, and by further providing a fluid bleed valve in said fluid passage means to regulate the transfer of air between the fuel bowl air section and the air intake air passage. This fluid bleed valve is operatively connected to the low pressure portion of the air intake passage and is responsive to the pressure therein to adjust the size of the fluid passage means and the air flow therethrough. Also provided is a pressure equalizing valve means which is conveniently associated with the accelerator plunger and operative to bring the pressure in the fuel bowl air section up to atmospheric pressure in response to sudden opening of the throttle valve for acceleration of the engine. To assist the operation of the control means a restriction is provided in the bowl vent states Patent 6 Patented. Sept. 26,. 1.961;.

ice

passage means is partially or completely opened by the:

bleed valve.

It is therefore a specific object of this invention to. provide a restriction in the bowl vent passage of a carburetor to allow an adjustable fluid bleed means to connect the fuel bowl air section to the carburetor air intake, passage to thereby adjust the pressure differential between the fuel bowl air section and the intake air passage during engine operating conditions of idle and low speeds and substantially closed choke position.

Afurther specific object of this invention is to provide the above carburetor having the aforementioned control means with a pressure equalizing valve means operative in response to sudden openingof the throttlevalve to suddenly increase the pressure in the fuel bowl air section relatively to the pressure in the intake air passage by allowing atmospheric air to bypass the restriction in the bowl vent passage.

Further objects and advantages of this invention will become apparent from the following description and drawings, in which:

FIGURE 1 represents a cross sectional view of adowndraft carburetor; and

FIGURE 2 represents a cross sectional view'taken along line 2-2 inthe direction of the arrows.

In FIGURE 1 is shown a typical downdraft carburetor 10 having an air intake passage designated generally as 12 comprising a high pressure intake portion 14 upstream of a thermostatically operated choke valve 16, an intermediate intake pressure portion 18 upstream of a throttle valve 20, and a low pressure intake portion 22 downstream of throttle valve 20. A typical carburetor fuel bowl generally designated 24 comprises an air section 26 communicating with the high pressure intake portion 14 through a bowl vent passage 28, and a fuel section 30 communicating with intermediate intake portion 18 through main fuel metering jet 32, main fuel passage-33; and main fuel port 34. Air atomizing passage 35 disperses. the fuel in air prior to its emission from port 34. A- conventional carburetor float valve generally designated 31, maintains the fuel at the proper level A in the fuel bowl 24. Restriction 36 in bowl vent passage 28 restrictsthe; air flowinto air section 26 for a purpose-describedbelowr A fluid bleed valve 38 is slidably mounted in a cylinder 4tlconnected through an air passage 42 to low pressureintake portion 22. A fluid passage 44in bleed valve 3.8 having restriction 39 therein connects with a fluid con-- duit 46 when valve 38- is in its down position as shown due to high vacuum in low pressure intake portion 22. and bleeds air from air section 26- of the fuel bowl through restriction 39 to the air passage'12' at a rate determined jointly by the sizes of restrictions 36 and 39 and by the relative premures in section 26,. andportions 14 and 18 to adjust the pressure differential between sec: tions 26 and 18 to provide the proper fuel flow main fuel jet 32. A spring 48 urges valve 38 upwardly. to disconnect conduits 44. and 46 during. relatively. high air pressure in portion 22 such as exists when choke. valve 16 and throttle valve 20 are open.

A pressure equalizing valve means or slot 50 isprovided in accelerator plunger 52 to bleed air into fuel bowl air section 26 as plunger 52 moves downwardby the force of spring 53 in response to opening of throttle. valve 2%. Throttle valve 20 is linked to plunger 52 by an arm 54 and connecting link 55 which progressively urge plunger 52 to an up position as accelerator valve 20 is moved to a closed position shownby the dotted lines in FIGURE 1. This slot 5! allows sufficient air to enteu fuel bowl section 26. to increase the pressure differential between section 26 and intake portion 18 to force suffiallow a lower than atmospheric pressure to cient fuel through metering jet 32 to compensate for the proportionately increased air flow through intake passage 12 in response to sudden opening of throttle valve for engine acceleration. The accelerator fuel chamber 56 is connected in the conventional manner through passage means 58 to the accelerator fuel jet 60 communicating with air intake passage 12. Accelerator air bleed 62 communicating with jet 60 is provided in the conventional manner to prevent low pressure in 18 from sucking fuel from said jet.

In a closed choke and closed throttle engine operating condition as shown, the air pumping action of the engine will suck sufficient air from intermediate air intake portion 18 to decrease the pressure therein and create a pressure drop across main fuel jet 32 of greater magnitude than exists during cold engine starting. However, the connection of conduits 44 and 46 due to low pressure in 22 will allow a portion of the air in section 26 to bleed into portion 18 of the air passage and reduce thereby the pressure drop and resultant fuel flow across jet 32. The restriction 36 in passage 28 will prevent the pressure in the fuel bowl air section 26 from increasing to atmospheric until such time as throttle 20 is opened to allow accelerator plunger 52 to move downwardly and bleed air through slot 50 into section 26 and cause an increased pressure drop and increased fuel flow across jet 32.

During idling of the engine and at low engine speeds a portion of the required fuel is delivered through idle fuel port 64 and low speed transfer port 66 in the conventional manner. These ports connect to the idle fuel jet 67 (FIGURE 2) through conduit 69 which is air bled by passage 71. Idle fuel adjusting needle 65 pro vides a further adjustment of the idle combustion mixture. The conventional secondary fuel jet 68 and secondary fuel regulating needle 70 connected to valve 38 for movement therewith provides further means for ad justing fuel flow to air intake passage 12 during engine operating conditions of idle and low speeds.

I claim:

1. In a carburetor having an air intake passage, a choke valve pivotally off center mounted in said passage and having means resiliently urging it to a position closing off said passage, a throttle valve operatively mounted in said air passage, a fuel bowl having an air section restrictively vented to the atmosphere and a fuel section communicating across a fuel jet with said passage intermediate said valves, conduit means connecting said air section to said passage intermediate said valves, and pressure responsive valve means in said conduit communicating with said passage downstream of said throttle valve and responsive to the pressure therein to adjust the fluid flow through said conduit and thereby the pressure differential between said air section and said passage intermediate said valves to thereby regulate the fuel flow through said jet.

2. Fuel feed control means for a carburetor having an intake air passage, a thermostatically controlled choke valve and a manually operable throttle valve operatively mounted in said air passage, a fuel bowl communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, said control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, adjustable fluid bleed means connecting said bowl vent passage to said intermediate portion to regulate the pressure differential between said fuel bowl and said intermediate portion, said bleed means being operatively connected to a low pressure portion of said air passage lying downstream of said throttle valve and responsive to low pressure therein to adjust said pressure differential.

3. Fuel feed control means for a carburetor having an intake air passage, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage to provide in said air passage a high pressure portion upstream of said choke valve an intermediate portion between said valves and a low pressure portion downstream of said throttle valve, a fuel bowl having an air section partially vented to the atmosphere and a fuel section communicating with said intermediate portion across a fuel jet, said fuel feed control means comprising an adjustable fluid bleed means operatively connected to said low pressure portion and adapted to connect said bowl air section to said intermediate portion of said air passage in response to low pressure in said low pressure portion to adjust the pressure differential between said bowl and said intermediate portion to thereby regulate the fuel flow through said fuel jet.

4. In a carburetor having an air intake passage, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage, a fuel bowl having an air section partially vented to the atmosphere and a fuel section communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, fuel feed control means comprising a bowl vent passage communicating with said air section of said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, and adjustable fluid bleed means having fluid conduit means connecting said bowl vent passage to said intermediate portion to regulate the pressure differential between said fuel bowl and said intermediate portion and a restriction in said bowl vent passage for further regulating said pressure differential.

5. Fuel feed control means for a carburetor having an intake air passage, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage, a fuel bowl communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, said control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, a restriction in said vent passage, fluid bleed means connected to a portion of said air passage and responsive to pressure therein to connect said bowl to said intermediate portion to regulate the pressure differential between said fuel bowl and said intermediate portion, and pressure equalizing valve means connected to said throttle valve and operative in response to sudden openings thereof to allow air to bypass said restriction to rapidly bring the pressure in said fuel bowl up to atmospheric pressure.

6. In a carburetor having an intake air passage, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage, a fuel bowl communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, a fuel feed control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, a restriction in said bowl vent passage, adjustable fluid bleed means connecting said bowl vent passage to said intermediate portion to regulate the pressure differential between said fuel bowl and said intermediate portion, said bleed means being operatively connected to a low pressure portion of said air passage lying downstream of said throttle valve and responsive to low pressure therein to adjust said pressure differential, and pressure equalizing valve means on said fuel bowl operative in response to opening of said throttle valve to decrease the pressure differential across said restriction in said bowl vent passage.

7. In a carburetor having an intake air passage, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage, a fuel bowl communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, fuel feed control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, a restriction in said bowl vent passage, adjustable fluid bleed means connecting said bowl vent passage to said intermediate portion to regulate the pressure difierential between said fuel bowl and said intermediate portion, said bleed means being operatively connected to a low pressure portion of said air passage lying downstream of said throttle valve and responsive to low pressure therein to adjust said pressure differential, and pressure equalizing valve means on said fuel bowl operatively connected to said throttle valve and operative in response to a predetermined degree of opening of said throttle valve to decrease the pressure differential across said restriction in said bowl vent passage.

8. Fuel feed control means for a carburetor having an intake air passage, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage, a fuel bowl communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, said control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, adjustable piston type fluid bleed means connecting said bowl vent passage to said intermediate portion to regulate the pressure differential between said fuel bowl and said intermediate portion, said bleed means being operatively connected to a low pressure portion of said air passage lying downstream of said throttle valve and responsive to low pressure therein to adjust said pressure differential.

9. Fuel feed control means for a carburetor having a body, an intake air passage in said body, a thermostatically controlled choke valve and a throttle valve peratively mounted in said air passage, a fuel bowl cornmunicating across a fuel jet with an inter-mediate portion of said air passage lying between said valves, said control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, a cylinder in said body communicating with said bowl vent passage, said intermediate portion and a low pressure portion of said air passage downstream of said throttle valve, and a piston reciprocably mounted in said cylinder and movable in response to low pressure in said low pressure portion to form a fluid passage from said intermediate portion to said bowl vent passage.

10. Fuel feed control means for a carburetor having a body, an intake air passage in said body, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage, a fuel bowl communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, said control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure 1n said high pressure portion to said fuel bowl, a cylinder in said body communicating with said bowl vent passage, said intermediate portion and a low pressure portion of said air passage downstream of said throttle valve, and a piston reciprocably mounted in said cylinder and movable in response to low pressure in said low pressure portion to form a fluid passage from said intermediate portion to said bowl vent passage, said piston being resiliently urged to a position in said cylinder tending to prevent a fluid transfer from said bowl vent passage to said intermediate portion.

11. Fuel feed control means for a carburetor having a body, an intake air passage in said body, a thermostatically controlled choke valve and a throttle valve operatively mounted in said air passage, a fuel 'bowl communicating across a fuel jet with an intermediate portion of said air passage lying between said valves, said control means comprising a bowl vent passage communicating with said bowl and with a high pressure portion of said air passage upstream of said choke valve and adapted to transmit the air pressure in said high pressure portion to said fuel bowl, a restriction in said bowl vent passage for regulating the air flow in said passage, a cylinder in said body communicating downstream of said restriction with said bowl vent passage, said intermediate portion and a low pressure portion of said air passage downstream of said throttle valve, and a piston reciprocably mounted in said cylinder and movable in response to low pressure in said low pressure portion to form a fluid passage from said intermediate portion to said bowl vent passage, said piston being resiliently urged to a position in said cylinder tending to prevent a fluid transfer from said bowl vent passage to said intermediate portion.

References Cited in the file of this patent UNITED STATES PATENTS 

